EP3205888A1 - Fluid pressure control device - Google Patents
Fluid pressure control device Download PDFInfo
- Publication number
- EP3205888A1 EP3205888A1 EP15849172.0A EP15849172A EP3205888A1 EP 3205888 A1 EP3205888 A1 EP 3205888A1 EP 15849172 A EP15849172 A EP 15849172A EP 3205888 A1 EP3205888 A1 EP 3205888A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pilot
- valve
- pressure
- chamber
- spool
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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- 239000012530 fluid Substances 0.000 title claims abstract description 39
- 230000007935 neutral effect Effects 0.000 claims description 13
- 101000793686 Homo sapiens Azurocidin Proteins 0.000 description 12
- 230000000694 effects Effects 0.000 description 10
- 230000004044 response Effects 0.000 description 7
- 238000007599 discharging Methods 0.000 description 6
- 230000004043 responsiveness Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000011144 upstream manufacturing Methods 0.000 description 5
- 230000008602 contraction Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000000717 retained effect Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 230000007774 longterm Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
- F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/01—Locking-valves or other detent i.e. load-holding devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/08—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K31/00—Actuating devices; Operating means; Releasing devices
- F16K31/12—Actuating devices; Operating means; Releasing devices actuated by fluid
- F16K31/36—Actuating devices; Operating means; Releasing devices actuated by fluid in which fluid from the circuit is constantly supplied to the fluid motor
- F16K31/38—Actuating devices; Operating means; Releasing devices actuated by fluid in which fluid from the circuit is constantly supplied to the fluid motor in which the fluid works directly on both sides of the fluid motor, one side being connected by means of a restricted passage and the motor being actuated by operating a discharge from that side
- F16K31/383—Actuating devices; Operating means; Releasing devices actuated by fluid in which fluid from the circuit is constantly supplied to the fluid motor in which the fluid works directly on both sides of the fluid motor, one side being connected by means of a restricted passage and the motor being actuated by operating a discharge from that side the fluid acting on a piston
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K51/00—Other details not peculiar to particular types of valves or cut-off apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/04—Special measures taken in connection with the properties of the fluid
- F15B21/044—Removal or measurement of undissolved gas, e.g. de-aeration, venting or bleeding
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/305—Directional control characterised by the type of valves
- F15B2211/30505—Non-return valves, i.e. check valves
- F15B2211/30515—Load holding valves
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/32—Directional control characterised by the type of actuation
- F15B2211/329—Directional control characterised by the type of actuation actuated by fluid pressure
Definitions
- the present invention relates to a fluid pressure control device including a load retaining mechanism that retains load pressure on a load-side pressure chamber of a fluid pressure cylinder.
- JP2004-60821A discloses a hydraulic circuit for controlling a boom cylinder of a hydraulic shovel.
- the hydraulic circuit includes a boom cylinder that extends and contracts by working oil supplied from a pump, a control valve that switches supply/discharge of the working oil to/from the boom cylinder, and a retaining valve circuit provided in a load pipeline of the boom cylinder.
- the retaining valve circuit has a retaining valve and a check valve that are connected in parallel.
- the check valve allows the working oil to flow only from the control valve to the load-side chamber of the boom cylinder.
- the retaining valve has an neutral position that disconnects the load-side chamber from the control valve, and a communication position that allow the load-side chamber to communicate with the control valve.
- the retaining valve is held in the neutral position by a biasing force of a spring, and is switched from the neutral position to the communication position as a spool moves against the biasing force of the spring by receiving the pilot pressure.
- the pilot pressure is supplied to the retaining valve in accordance with an operated amount. This causes the retaining valve to open, whereby the working oil in the load-side chamber of the boom cylinder flows to the control valve via the retaining valve. By this, the boom cylinder contracts.
- a structure In order to remove the air in the pilot chamber, a structure can be considered in which an orifice or a gap is provided between the pilot chamber and the drain passage of the working oil.
- the pilot pressure in the pilot chamber is constantly drained to the drain passage. This causes unstableness to the pilot pressure, and may cause a response delay and variable response, at a time of slight operation of the retaining valve.
- An object of the present invention is to provide a fluid pressure control device including a load retaining mechanism capable of removing air inside the pilot chamber while being able to suppress an effect given on responsiveness.
- a fluid pressure control device includes a cylinder configured to extend and contract by working fluid supplied from a pump to drive a load, a control valve configured to switch supply/discharge of the working fluid to/from the cylinder to control the extending and contracting of the cylinder, a pilot valve configured to lead pilot pressure to the control valve, a main passage configured to connect the control valve and a load-side pressure chamber of the cylinder to which load pressure acts due to the load when the control valve is in a neutral position, and a load retaining mechanism disposed on the main passage and configured to retain load pressure in the load-side pressure chamber when the control valve is in the neutral position, wherein the load retaining mechanism includes a check valve configured to allow the working fluid to flow only from the control valve to the load-side pressure chamber, a bypass passage configured to lead the working fluid in the load-side pressure chamber to the control valve by bypassing the check valve, and a switching valve disposed on the bypass passage and configured to switch an opened or closed state of the bypass passage, the switching valve
- a hydraulic control device 100 serving as a fluid pressure control device controls operations of a hydraulic work machine such as a hydraulic shovel.
- the hydraulic control device 100 controls extending and contracting movements of a cylinder 2 that drives an arm 1 serving as a load of the hydraulic shovel shown in Fig. 1 .
- the cylinder 2 is partitioned into a rod-side pressure chamber 2a and a counter rod-side pressure chamber 2b by a piston rod 3 that slidably moves within the cylinder 2.
- An engine is installed into the hydraulic shovel, and by the power of the engine are driven a pump 4 and a pilot pump 5 that serve as hydraulic sources.
- Working oil (working fluid) that is discharged from the pump 4 is supplied to the cylinder 2 via a control valve 6.
- the control valve 6 and the rod-side pressure chamber 2a of the cylinder 2 are connected by a first main passage 7 serving as a main passage, and the control valve 6 and the counter rod-side pressure chamber 2b of the cylinder 2 are connected by a second main passage 8.
- the control valve 6 is operated by pilot pressure oil supplied to the pilot chambers 6a and 6b.
- the pilot pressure oil is supplied to the pilot chambers 6a and 6b from the pilot pump 5 via a pilot valve 10 in response to manual operation of an operation lever 9 by an operator of the hydraulic shovel.
- the control valve 6 switches to position 6A.
- Working oil from the pump 4 is supplied to the rod-side pressure chamber 2a via the first main passage 7, and working oil in the counter rod-side pressure chamber 2b is discharged to a tank T via the second main passage 8. This causes the cylinder 2 to contract, and the arm 1 lifts up in a direction of arrow A shown in Fig. 1 .
- the control valve 6 switches to position 6B.
- the working oil from the pump 4 is supplied to the counter rod-side pressure chamber 2b via the second main passage 8, and the working oil in the rod-side pressure chamber 2a is discharged to the tank T via the first main passage 7. This causes the cylinder 2 to extend, and the arm 1 descends in a direction of arrow B shown in Fig. 1 .
- control valve 6 switches to position 6C.
- the supply/discharge of the working oil to/from the cylinder 2 is discontinued, and the arm 1 is kept in a stopped state.
- control valve 6 includes three switching positions, i.e., a contraction position 6A in which the cylinder 2 is contracted, an extension position 6B in which the cylinder 2 is extended, and an neutral position 6C in which the load of the cylinder 2 is retained. Furthermore, the control valve 6 controls the extension and contraction of the cylinder 2 by switching the supply and discharge of the working oil to/from the cylinder 2.
- the rod-side pressure chamber 2a serves as a load-side pressure chamber on which load pressure acts in the case in which the control valve 6 is in the neutral position 6C.
- a load retaining mechanism 20 is disposed in the first main passage 7 connected to the load-side pressure chamber, that is, the rod-side pressure chamber 2a.
- the load retaining mechanism 20 retains the load pressure in the rod-side pressure chamber 2a when the control valve 6 is in the neutral position 6C. As shown in Fig. 1 , the load retaining mechanism 20 is fixed to the surface of the cylinder 2.
- a counter rod-side pressure chamber 16b serves as the load-side pressure chamber. Therefore, when providing the load retaining mechanism 20 to the boom 12, the load retaining mechanism 20 is disposed on the main passage connected to the counter rod-side pressure chamber 16b (see Fig. 1 ).
- the load retaining mechanism 20 includes a check valve 21 disposed on the first main passage 7, and a switching valve 22 that operates in connection with the control valve 6 by pilot pressure oil supplied to a first pilot chamber 22a serving as the pilot chamber, via the pilot valve 10.
- the check valve 21 allows the working oil to flow from the control valve 6 to the rod-side pressure chamber 2a, while restricting the flow of the working oil from the rod-side pressure chamber 2a to the control valve 6. That is to say, the check valve 21 prevents the working oil in the rod-side pressure chamber 2a from leaking and retains the load pressure, and keeps the stopped state of the arm 1.
- the switching valve 22 is disposed in a bypass passage 23 that leads working oil on the side of the rod-side pressure chamber 2a with respect to the check valve 21 to the side of the control valve 6 with respect to the check valve 21, by bypassing the check valve 21.
- the switching valve 22 switches an opened or closed state of the bypass passage 23 in accordance with the pilot pressure supplied to the first pilot chamber 22a, and controls the flow of the working oil in the first main passage 7 when extending the cylinder 2.
- pilot pressure When pilot pressure is leaded to the pilot chamber 6b of the control valve 6, pilot pressure of identical pressure is leaded simultaneously to the first pilot chamber 22a. That is to say, when the control valve 6 is switched to the extension position 6B, the switching valve 22 also opens.
- the switching valve 22 maintains a disconnected state by an biasing force of a spring 24, and the bypass passage 23 is disconnected.
- a relief passage 25 branches from and is connected to an upstream of the check valve 21 on the first main passage 7.
- the relief passage 25 disposes a relief valve 26 that opens when pressure in the rod-side pressure chamber 2a reaches a predetermined pressure and allows working oil to flow therethrough, and releases the working oil in the rod-side pressure chamber 2a.
- the working oil that passes through the relief valve 26 is discharged to the tank T via the discharging passage 27.
- An orifice 28 is disposed on the discharging passage 27, and pressure upstream of the orifice 28 is leaded to a second pilot chamber 22b. That is to say, the switching valve 22 also opens by the pressure of relief pressure oil leaded through the relief valve 26 to the second pilot chamber 22b.
- a first main relief valve 13 is connected on the side of the control valve 6 with respect to the check valve 21 in the first main passage 7, and the second main passage 8 is connected to a second main relief valve 14.
- the check valve 21 is assembled in a body 30.
- the body 30 is formed having a sliding hole 30a, and in the sliding hole 30a, a valve element 31 of the check valve 21 is slidably assembled.
- the sliding hole 30a is formed penetrating through the body 30.
- One end (upstream end) of the sliding hole 30a is connected to the first main passage 7 on the side of the cylinder 2 via a plug 32, and the other end (downstream end) thereof is connected to the first main passage 7 on the side of the control valve 6 via a plug 33.
- a seat portion 34 is formed, which decreases in diameter as it progresses downstream.
- the valve element 31 is constantly pressed in a direction sitting on the seat portion 34, by biasing force of a spring 35 disposed between the valve element 31 and the plug 32.
- the check valve 21 maintains a closed state with respect to the working oil flowing from the first main passage 7 on the side of the cylinder 2. Moreover, the check valve 21 opens when the valve element 31 receives a force exceeding the biasing force of the spring 35 by the pressure of the working oil flowing from the first main passage 7 on the side of the control valve 6.
- the switching valve 22 is assembled inside the body 30.
- a spool hole 30b is formed in the body 30, and a spool 36 is assembled slidably in the spool hole 30b.
- a spring chamber 38 is defined by a cap 37.
- the spring chamber 38 communicates with a drain passage 40 (see Fig. 2 ) via a drain port 39a formed in a plug 39 that screws to an opening of the cap 37.
- the drain passage 40 communicates with a downstream of the orifice 28 in a discharging passage 27 (see Fig. 2 ) and connects to the tank T.
- the spring chamber 38 accommodates a spring 41 serving as an biasing member for biasing the spool 36. Moreover, the spring chamber 38 accommodates an annular first spring holding member 42 whose end plane abuts one end plane of the spool 36, and an annular second spring holding member 43 that abuts a tip surface of the plug 39 screwed to the cap 37.
- the spring 41 is disposed in a compressed state between the first spring holding member 42 and the second spring holding member 43, and biases the spool 36 in the valve-closing direction via the first spring holding member 42.
- the pilot chambers 22a and 22b are defined by the piston hole 30c and cap 44.
- the piston hole 30c is formed in communication with the spool hole 30b.
- the cap 44 closes the piston hole 30c.
- a piston 45 is inserted slidably inside the pilot chambers 22a and 22b.
- the piston 45 includes a rear plane receiving pilot pressure, and applies thrust against the biasing force of the spring 41 to the spool 36 when the rea plane receives the pilot pressure.
- the pilot chambers 22a and 22b are partitioned by the piston 45 into a first pilot chamber 22a facing the rear plane of the piston 45 and a second pilot chamber 22b facing the front plane of the piston 45 and the other end plane 36b of the spool 36.
- the first pilot chamber 22a is supplied with pilot pressure oil from the pilot valve 10 via a pilot port 44a formed in the cap 44.
- Leaded to the second pilot chamber 22b is relief valve oil having passed through the relief valve 26 via the discharging passage 27.
- the piston 45 includes a sliding portion 45a whose outer circumferential surface slides along an inner circumferential surface of the piston hole 30c, a tip portion 45b facing the other end plane 36b of the spool 36, a groove portion 45c formed across the front plane of the piston 45 in a radial direction, and a conduction path 46 that allows the first pilot chamber 22a to communicate with the second pilot chamber 22b.
- the tip portion 45b is formed having a smaller diameter than that of the sliding portion 45a.
- the conduction path 46 is provided pierced through the sliding portion 45a.
- the conduction path 46 includes an axial direction passage 46a defined by a hole pierced through from an end plane of the sliding portion 45a on the side of the cap 44 to around a center of the sliding portion 45a towards the tip portion 45b in an axial direction, a radial direction passage 46b defined by a hole pierced through from a tip of the axial direction passage 46a in a radial direction to penetrate through the sliding portion 45a, and an air removing throttle 46c defined by a hole provided at a joining part at the tip of the axial direction passage 46a with the radial direction passage 46b.
- pilot pressure oil When pilot pressure oil is supplied in the first pilot chamber 22a via the pilot port 44a, the pilot pressure acts on the rear plane of the sliding portion 45a. This causes the piston 45 to move forward, which makes the tip portion 45b contact the other end plane 36b of the spool 36 and make the spool 36 move. As such, the spool 36 receives the thrust of the piston 45 generated based on the pilot pressure acting on the rear plane of the piston 45, and moves in the valve-opening direction against the biasing force of the spring 41.
- the spool 36 stops at a position in which the biasing force of the spring 41 acting on one end plane 36a is balanced with the thrust of the piston 45 acting on the other end plane 36b, and an aperture of the switching valve 22 is defined in accordance with the stopped position of the spool 36.
- the spool 36 moves in the valve-opening direction when the thrust of the piston 45 is greater than the biasing force of the spring 41, and moves in the valve-closing direction when the biasing force of the spring 41 is greater than the thrust of the piston 45.
- the outer circumferential surface of the spool 36 is partially cut off annularly, and a poppet portion 47, a first land portion 48, and a second land portion 49 are formed in the order from the tip side in the valve-opening direction.
- the poppet portion 47 has an outer diameter greater than those of the first land portion 48 and the second land portion 49, and is formed in a tapered manner with its outer diameter increasing as it advances in the valve-opening direction.
- the inner circumferential surface of the spool hole 30b is partially cut off annularly, and with this cut off parts and the outer circumferential surface of the spool 36, a first pressure chamber 50, a second pressure chamber 51, and a third pressure chamber 52 are formed in order from the tip side in the valve-opening direction.
- the body 30 is formed having a first communication passage 53 that allows the first pressure chamber 50 to communicate with the first main passage 7, and a second communication passage 54 that allows the third pressure chamber 52 to communicate with the first main passage 7.
- the first communication passage 53 communicates with a downstream of the seat portion 34 of the check valve 21 in the first main passage 7, and the second communication passage 54 communicates with an upstream of the seat portion 34 of the check valve 21 in the first main passage 7.
- the first communication passage 53 and the second communication passage 54 form the bypass passage 23 together with the spool hole 30b.
- the first pressure chamber 50 constantly communicates with the first main passage 7 at downstream of the seat portion 34 of the check valve 21.
- the second pressure chamber 51 is disconnected from the first pressure chamber 50 when the poppet portion 47 is seated on an annular projecting portion 55 projecting annularly inside in the radial direction from the inner circumferential surface of the spool hole 30b.
- the third pressure chamber 52 communicates constantly with am upstream of the seat portion 34 of the check valve 21 in the first main passage 7.
- a plurality of notches 56 are formed on the outer circumference of the first land portion 48 of the spool 36.
- the notches 56 allow the third pressure chamber 52 to communicate with the second pressure chamber 51 when the spool 36 moves in the valve-opening direction.
- the second pilot chamber 22b is constantly communicated with the spring chamber 38 via a conduction hole 57 formed in the axial direction inside the spool 36, and a throttle passage 58.
- One end of the conduction hole 57 opens to the second pilot chamber 22b, and the other end is located in the vicinity of the spring chamber 38.
- the opening of the throttle passage 58 reaches an expanded diameter portion 59 of the cap 37.
- the inner circumferential plane of the cap 37 is formed with a larger diameter.
- Fig. 6A is a partially enlarged view showing the piston 45 of Fig. 4 in an enlarged manner.
- the inner diameter of the second pilot chamber 22b is slightly larger than the outer diameter of a sliding portion 45a of the piston 45.
- the opening of the radial direction passage 46b of the piston 45 has not reached the second pilot chamber 22b. Therefore, the pilot pressure oil that is leaded to the first pilot chamber 22a remains in the first pilot chamber 22a without leaking into the second pilot chamber 22b. Therefore, in this state, the pilot pressure oil in the first pilot chamber 22a does not flow into the spring chamber 38 via the conduction hole 57 and the throttle passage 58.
- the second pilot chamber 22b is continuously maintained in the communicated state with the spring chamber 38 via the conduction hole 57 and the throttle passage 58.
- Fig. 6B is a partially enlarged view showing the piston 45 of Fig. 5 in an enlarged manner.
- the opening of the radial direction passage 46b of the piston 45 opens to the second pilot chamber 22b.
- This causes the pilot pressure oil leaded to the first pilot chamber 22a to be leaded to the second pilot chamber 22b via the axial direction passage 46a and the radial direction passage 46b.
- the flow of the pilot pressure oil is throttled by the air removing throttle 46c provided between the axial direction passage 46a and the radial direction passage 46b, the pilot pressure in the first pilot chamber 22a is maintained at a predetermined pilot pressure.
- the pilot pressure oil that is leaded to the second pilot chamber 22b is leaded to the conduction hole 57 inside the spool hole 30b via the groove portion 45c formed on the front plane of the piston 45. Furthermore, as shown in Fig. 5 , the pilot pressure oil is leaded from the conduction hole 57 to the spring chamber 38 via the throttle passage 58, and is discharged to the drain passage 40 via the drain port 39a.
- the opening of the radial direction passage 46b of the piston 45 starts to open to the second pilot chamber 22b.
- This predetermined stroke amount is defined by a position that the radial direction passage 46b is formed.
- the predetermined stroke amount is set as a stroke amount slightly smaller than the stroke amount equivalent to a full stroke of the piston 45.
- the control valve 6 switches to the extension position 6B by the amount in accordance with the pilot pressure. Moreover, simultaneously to this, the pilot pressure is also leaded to the first pilot chamber 22a; accordingly, the switching valve 22 opens in accordance with the supplied pilot pressure.
- the bypass passage 23 is released by this, and thus the working oil in the rod-side pressure chamber 2a is leaded to the control valve 6 by bypassing the check valve 21 from the first main passage 7, and is discharged from the control valve 6 to the tank T. Moreover, the working oil that is discharged by the pump 4 is supplied to the counter rod-side pressure chamber 2b, and thus the cylinder 2 extends. This causes the arm 1 to descend in the direction of arrow B shown in Fig. 1 .
- air is mixed inside the first pilot chamber 22a to which the pilot pressure is supplied. Moreover, air may also similarly mix therein after maintenance and long-term storage of the hydraulic shovel.
- the pilot pressure oil When the pilot pressure oil is leaded to the first pilot chamber 22a of the switching valve 22 by the lever operation of the operator in this state, the pilot pressure in the first pilot chamber 22a varies due to the volume change of the air, and may cause a response delay in the movement of the spool 36. This may cause a decrease in the operability of the cylinder 2.
- a structure can be considered in which the first pilot chamber 22a constantly communicates with the second pilot chamber 22b.
- the pilot pressure oil in the first pilot chamber 22a will constantly drain to the drain passage 40 even after the air is discharged upon movement of the spool 36 by a predetermined stroke amount or more. Therefore, the pilot pressure may become unstable. Particularly when performing an operation such as an inching operation in which lever operated amount by the operator is minute, this may cause a response delay or a variation in responsiveness in the opening and closing operation of the switching valve 22.
- the conduction path 46 that allows the first pilot chamber 22a to communicate with the second pilot chamber 22b is provided in the piston 45. Furthermore, the conduction path 46 opens when the stroke amount of the piston 45 becomes equal to or more than the predetermined stroke amount that is slightly smaller than the full stroke amount.
- the switching valve 22 includes a conduction path 46 that leads one part of the pilot pressure oil leaded to the first pilot chamber 22a, to the drain passage 40.
- the conduction path 46 communicates with the drain passage 40 when the piston 45 of the switching valve 22 moves by the predetermined stroke amount or more in the valve-opening direction. Therefore, at the time of slight operation in which the stroke amount of the switching valve 22 is small, the variation in the pilot pressure can be prevented, and when the stroke amount of the switching valve 22 is large, the air that is mixed in the first pilot chamber 22a can be discharged to the drain passage 40. Thus, air removal of the first pilot chamber 22a is possible while holding down the effect on the responsiveness.
- the switching valve 22 includes the piston 45 that presses the spool 36 in the valve-opening direction in receiving the pilot pressure in the first pilot chamber 22a, and the conduction path 46 that allows the first pilot chamber 22a to communicate with the second pilot chamber 22b is formed in the piston 45. Therefore, the air removal can be performed without making the structure of the spool complex.
- the structure of a conduction path 146 differs from the first embodiment.
- the conduction hole 57 that allows the second pilot chamber 22b to communicate with the spring chamber 38 is formed inside the spool 36, whereas in the present embodiment, a conduction hole 157 is newly formed in the body 30.
- One end (downstream end) of this conduction hole 157 is connected to a throttle passage 158 that allows the inside of the cap 37 to communicate with the outside of the cap 37 screwed to the body 30. This makes the second pilot chamber 22b communicate with the drain port 39a via the conduction hole 157, the throttle passage 158 and the spring chamber 38.
- the conduction path 146 is formed on the outer circumferential surface of the sliding portion 45a of the piston 45.
- Fig. 9A is a partially enlarged view showing the piston 45 of Fig. 7 in an enlarged manner.
- the conduction path 146 includes a spiral groove 146a serving as a groove formed in a spiral form on the outer circumferential surface of the sliding portion 45a of the piston 45, and a small diameter portion 146b serving as a groove formed on the outer circumferential surface of the sliding portion 45a.
- the small diameter portion 146b is connected to a terminal of the spiral groove 146a on the side of the piston front plane (left side in Fig. 9A ).
- the small diameter portion 146b has a smaller diameter than that of the outer circumferential surface of the sliding portion 45a.
- a cross sectional shape of the spiral groove 146a may be formed rectangular as shown in Fig. 9B , or may be formed in a V-shape as shown in Fig. 9C .
- the spiral groove 146a is sufficiently small in its cross section, and also functions as a throttle.
- the pilot pressure oil that is leaded to the second pilot chamber 22b is leaded to the spring chamber 38 via the conduction hole 157 formed in the body 30 and the throttle passage 158 formed in the cap 37, and is leaded to the drain passage 40 via the drain port 39a.
- the small diameter portion 146b of the piston 45 starts to open to the second pilot chamber 22b.
- This predetermined stroke amount is defined by the position that the small diameter portion 146b is formed.
- the predetermined stroke amount is set as a stroke amount slightly smaller than the stroke amount equivalent to a full stroke of the piston 45.
- the conduction path 146 is formed on the outer circumferential surface of the piston 45, the conduction path 146 can be formed just by forming a groove on the outer circumferential surface of the piston 45 with an end mill or like device. This facilitates the forming of the conduction path 146, and allows for reducing manufacturing costs.
- the spool 36 and the piston 45 are formed as separate bodies, whereas in the present embodiment, the piston 45 and the piston hole 30c are omitted, and a spool hole 230b and a spool 236 extend in the axial direction. That is to say, the spool hole 230b communicates with the first pilot chamber 22a, and the other end plane 236b of the spool 236 faces the first pilot chamber 22a.
- the conduction hole 57 that allows the second pilot chamber 22b to communicate with the spring chamber 38 is formed inside the spool 36, whereas in the present embodiment, a conduction hole 257 is newly formed in the body 30.
- One end (downstream end) of this conduction hole 257 is connected to a throttle passage 258 that allows the inside of the cap 37 to communicate with the outside the cap 37 screwed to the body 30.
- the working oil that has passed through the relief valve 26 is leaded to the second pilot chamber 22b, whereas in the present embodiment, instead of the pilot chamber 22b, a large diameter portion 61 is newly provided, which portion is formed by annularly cutting off the inner circumferential surface of the spool hole 230b.
- the working oil that has passed through the relief valve 26 is constantly leaded to the conduction hole 257 regardless of the axial direction position of the spool 236, and is leaded to the drain port 39a via the throttle passage 258 and the spring chamber 38.
- Fig. 14 shows the hydraulic circuit diagram of the first embodiment. That is to say, the working oil that has passed through the relief valve 26 is constantly discharged to the tank T, without acting on the switching valve 22.
- Fig. 14 members having the same functions as those in Fig. 2 are provided with identical reference signs.
- the conduction path 246 is pierced through the inside of the spool 236. More specifically, the conduction path 246 includes an axial direction passage 246a defined by a hole pierced through in the axial direction from the other end plane 236b serving as a pressure receiving plane of the spool 36 to an one end plane 236a, a radial direction passage 246b defined by a hole pierced through in a radial direction from the tip of the axial direction passage 246a and penetrating through the spool 236, and an air removing throttle 246c defined by a hole provided at a joining part with the radial direction passage 246b at the tip of the axial direction passage 246a.
- the opening of the radial direction passage 246b of the spool 236 opens to the large diameter portion 61. This allows the pilot pressure oil leaded to the first pilot chamber 22a to be leaded to the large diameter portion 61 via the conduction path 246. Meanwhile, since the flow of the pilot pressure oil is throttled by the air removing throttle 246c, the pilot pressure in the first pilot chamber 22a is maintained at the predetermined pilot pressure.
- the pilot pressure oil that is leaded to the large diameter portion 61 is leaded to the spring chamber 38 via the conduction hole 257 formed in the body 30 and the throttle passage 258 formed in the cap 37, and is leaded to the drain passage 40 via the drain port 39a.
- the radial direction passage 246b of the spool 236 starts to open to the large diameter portion 61.
- This predetermined stroke amount is defined by the position that the radial direction passage 246b is formed.
- the predetermined stroke amount is set to a stroke amount slightly smaller than a stroke amount equivalent to the full stroke of the spool 236.
- the other end plane 236b of the spool 236 receives the pilot pressure from the first pilot chamber 22a and the spool 236 moves in the valve-opening direction, and thus there is no need to provide a piston for receiving the pilot pressure. Therefore, the number of parts can be reduced.
- the conduction path 246 is pierced through inside the spool 236, it is possible to prevent the pilot pressure oil from leaking via the outer circumference of the spool 236 from the conduction path 246 before the stroke amount of the spool 236 reaches the predetermined stroke amount.
- air removal of the first pilot chamber 22a is possible while securely suppress the effect on the responsiveness.
- the conduction hole 257 is formed in the body 30, this allows for simplifying the structure of the spool 236, and allows for reducing manufacturing costs.
- the structure of a conduction path 346 differs from that of the third embodiment, however other structures are identical to the third embodiment.
- the conduction path 346 is formed on the outer circumferential surface of the spool 36.
- the conduction path 346 includes a spiral groove 346a serving as a groove formed in a spiral form on the outer circumferential surface of the spool 36, and a small diameter portion 346b serving as a groove formed on the outer circumferential surface of the spool 36.
- the small diameter portion 346b is connected to a terminal of the spiral groove 346a on the stroke side (left side in Fig. 12 ) of the spool 36.
- the small diameter portion 346b has a smaller diameter than that of the outer circumferential surface of the spool 336.
- the cross section of the spiral groove 346a may be formed in a rectangular shape as with the spiral groove 14a shown in Fig. 9B , or may be formed in a V-shape as with the spiral groove 14a shown in Fig. 9C .
- the spiral groove 346a is sufficiently small in its cross section, and also functions as a throttle.
- the pilot pressure oil that is leaded to the large diameter portion 61 is leaded to the conduction hole 257 formed in the body 30, and is discharged to the drain passage 40 via the throttle passage 258 formed in the cap 37, the spring chamber 38, and the drain port 39a.
- the small diameter portion 346b of the spool 36 starts to open to the large diameter portion 61.
- This predetermined stroke amount is defined by the position that the small diameter portion 346b is formed.
- the predetermined stroke amount is set to a stroke amount slightly smaller than a stroke amount equivalent to the full stroke of the spool 336.
- the conduction path 346 is formed on the outer circumferential surface of the spool 336. Accordingly, the conduction path 346 can be formed just by forming a groove on the outer circumferential surface of the spool 336 with an end mill or like device. This facilitates the forming of the conduction path 346, and allows for reducing manufacturing costs.
- the working fluid may be liquid other than oil, for example water or an alternate water-soluble liquid.
- the spring 41 is exemplified as the biasing member, however this may be any other extendable member that can bias the spool.
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Abstract
Description
- The present invention relates to a fluid pressure control device including a load retaining mechanism that retains load pressure on a load-side pressure chamber of a fluid pressure cylinder.
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JP2004-60821A - The retaining valve circuit has a retaining valve and a check valve that are connected in parallel. The check valve allows the working oil to flow only from the control valve to the load-side chamber of the boom cylinder. The retaining valve has an neutral position that disconnects the load-side chamber from the control valve, and a communication position that allow the load-side chamber to communicate with the control valve. The retaining valve is held in the neutral position by a biasing force of a spring, and is switched from the neutral position to the communication position as a spool moves against the biasing force of the spring by receiving the pilot pressure.
- When the operator operates the remote control valve in a state in which the boom cylinder is retained at a predetermined operation position by the retaining valve, the pilot pressure is supplied to the retaining valve in accordance with an operated amount. This causes the retaining valve to open, whereby the working oil in the load-side chamber of the boom cylinder flows to the control valve via the retaining valve. By this, the boom cylinder contracts.
- In a manufacturing stage of the hydraulic shovel, more specifically, in a stage in which the retaining valve is attached to the hydraulic shovel and the pilot passage is connected to the retaining valve, air is mixed inside the pilot chamber of the retaining valve to which the pilot pressure is supplied. When the retaining valve is switched from the neutral position to the communication position due to a lever operation by an operator in this state, a response delay in the movement of the spool may occur and may worsen operability of the boom cylinder.
- In order to remove the air in the pilot chamber, a structure can be considered in which an orifice or a gap is provided between the pilot chamber and the drain passage of the working oil. However, with such a structure, the pilot pressure in the pilot chamber is constantly drained to the drain passage. This causes unstableness to the pilot pressure, and may cause a response delay and variable response, at a time of slight operation of the retaining valve.
- An object of the present invention is to provide a fluid pressure control device including a load retaining mechanism capable of removing air inside the pilot chamber while being able to suppress an effect given on responsiveness.
- According to one aspect of the present invention, a fluid pressure control device includes a cylinder configured to extend and contract by working fluid supplied from a pump to drive a load, a control valve configured to switch supply/discharge of the working fluid to/from the cylinder to control the extending and contracting of the cylinder, a pilot valve configured to lead pilot pressure to the control valve, a main passage configured to connect the control valve and a load-side pressure chamber of the cylinder to which load pressure acts due to the load when the control valve is in a neutral position, and a load retaining mechanism disposed on the main passage and configured to retain load pressure in the load-side pressure chamber when the control valve is in the neutral position, wherein the load retaining mechanism includes a check valve configured to allow the working fluid to flow only from the control valve to the load-side pressure chamber, a bypass passage configured to lead the working fluid in the load-side pressure chamber to the control valve by bypassing the check valve, and a switching valve disposed on the bypass passage and configured to switch an opened or closed state of the bypass passage, the switching valve includes a pilot chamber to which pilot pressure is leaded via the pilot valve, a spool configured to move in a valve-opening direction in accordance with the pilot pressure in the pilot chamber, a biasing member configured to bias the spool in a valve-closing direction, and a conduction path configured to lead one part of a pilot pressure fluid leaded to the pilot chamber, to a drain passage, the conduction path is configured to communicate with the drain passage, when the switching valve moves by a predetermined stroke amount or more in the valve-opening direction.
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Fig. 1 is a view showing one part of a hydraulic shovel. -
Fig. 2 is a hydraulic circuit diagram of a fluid pressure control device according to a first embodiment of the present invention. -
Fig. 3 is a sectional view of a load retaining mechanism of a fluid pressure control device according to the first embodiment of the present invention. -
Fig. 4 is a sectional view of the load retaining mechanism of a fluid pressure control device according to the first embodiment of the present invention. -
Fig. 5 is a sectional view of the load retaining mechanism of a fluid pressure control device according to the first embodiment of the present invention. -
Fig. 6A is an enlarged view showing a piston of a switching valve in an enlarged manner. -
Fig. 6B is an enlarged view showing a piston of a switching valve in an enlarged manner. -
Fig. 7 is a sectional view of a load retaining mechanism of a fluid pressure control device according to a second embodiment of the present invention. -
Fig. 8 is a sectional view of the load retaining mechanism of a fluid pressure control device according to the second embodiment of the present invention. -
Fig. 9A is a side view showing a groove formed on an outer circumferential surface of a piston. -
Fig. 9B is a partial sectional view showing a cross sectional shape of the groove formed on the outer circumferential surface of the piston. -
Fig. 9C is partial sectional view showing a cross sectional shape of the groove formed on the outer circumferential surface of the piston. -
Fig. 10 is a sectional view of a load retaining mechanism of a fluid pressure control device according to a third embodiment of the present invention. -
Fig. 11 is a sectional view of a load retaining mechanism of a fluid pressure control device according to the third embodiment of the present invention. -
Fig. 12 is a sectional view of a load retaining mechanism of a fluid pressure control device according to a fourth embodiment of the present invention. -
Fig. 13 is a sectional view of the load retaining mechanism of a fluid pressure control device according to the fourth embodiment of the present invention. -
Fig. 14 is a hydraulic circuit diagram of a fluid pressure control device according to the third embodiment of the present invention. - Embodiments of the present invention will be described with reference to the drawings. Identical reference signs provided between different drawings will represent identical configurations.
- First, a first embodiment will be described.
- A
hydraulic control device 100 serving as a fluid pressure control device controls operations of a hydraulic work machine such as a hydraulic shovel. In the present embodiment, thehydraulic control device 100 controls extending and contracting movements of acylinder 2 that drives an arm 1 serving as a load of the hydraulic shovel shown inFig. 1 . - First, a hydraulic circuit of the
hydraulic control device 100 is described with reference toFig. 2 . - The
cylinder 2 is partitioned into a rod-side pressure chamber 2a and a counter rod-side pressure chamber 2b by apiston rod 3 that slidably moves within thecylinder 2. - An engine is installed into the hydraulic shovel, and by the power of the engine are driven a pump 4 and a
pilot pump 5 that serve as hydraulic sources. - Working oil (working fluid) that is discharged from the pump 4 is supplied to the
cylinder 2 via acontrol valve 6. - The
control valve 6 and the rod-side pressure chamber 2a of thecylinder 2 are connected by a firstmain passage 7 serving as a main passage, and thecontrol valve 6 and the counter rod-side pressure chamber 2b of thecylinder 2 are connected by a secondmain passage 8. - The
control valve 6 is operated by pilot pressure oil supplied to thepilot chambers pilot chambers pilot pump 5 via apilot valve 10 in response to manual operation of an operation lever 9 by an operator of the hydraulic shovel. - More specifically, when pilot pressure is leaded to the
pilot chamber 6a, thecontrol valve 6 switches to position 6A. Working oil from the pump 4 is supplied to the rod-side pressure chamber 2a via the firstmain passage 7, and working oil in the counter rod-side pressure chamber 2b is discharged to a tank T via the secondmain passage 8. This causes thecylinder 2 to contract, and the arm 1 lifts up in a direction of arrow A shown inFig. 1 . - On the other hand, when the pilot pressure is leaded to the
pilot chamber 6b, thecontrol valve 6 switches to position 6B. The working oil from the pump 4 is supplied to the counter rod-side pressure chamber 2b via the secondmain passage 8, and the working oil in the rod-side pressure chamber 2a is discharged to the tank T via the firstmain passage 7. This causes thecylinder 2 to extend, and the arm 1 descends in a direction of arrow B shown inFig. 1 . - When no pilot pressure is leaded to the
pilot chambers control valve 6 switches to position 6C. The supply/discharge of the working oil to/from thecylinder 2 is discontinued, and the arm 1 is kept in a stopped state. - As such, the
control valve 6 includes three switching positions, i.e., acontraction position 6A in which thecylinder 2 is contracted, anextension position 6B in which thecylinder 2 is extended, and anneutral position 6C in which the load of thecylinder 2 is retained. Furthermore, thecontrol valve 6 controls the extension and contraction of thecylinder 2 by switching the supply and discharge of the working oil to/from thecylinder 2. - As shown in
Fig. 1 , when thecontrol valve 6 is switched to theneutral position 6C while thebucket 11 is lifted and the movement of the arm 1 is stopped, force in the extending direction acts on thecylinder 2 due to the dead load of members such as thebucket 11 and the arm 1. As such, in thecylinder 2 that drives the arm 1, the rod-side pressure chamber 2a serves as a load-side pressure chamber on which load pressure acts in the case in which thecontrol valve 6 is in theneutral position 6C. - A
load retaining mechanism 20 is disposed in the firstmain passage 7 connected to the load-side pressure chamber, that is, the rod-side pressure chamber 2a. Theload retaining mechanism 20 retains the load pressure in the rod-side pressure chamber 2a when thecontrol valve 6 is in theneutral position 6C. As shown inFig. 1 , theload retaining mechanism 20 is fixed to the surface of thecylinder 2. - In a
cylinder 16 that drives aboom 12, a counter rod-side pressure chamber 16b serves as the load-side pressure chamber. Therefore, when providing theload retaining mechanism 20 to theboom 12, theload retaining mechanism 20 is disposed on the main passage connected to the counter rod-side pressure chamber 16b (seeFig. 1 ). - The
load retaining mechanism 20 includes acheck valve 21 disposed on the firstmain passage 7, and a switchingvalve 22 that operates in connection with thecontrol valve 6 by pilot pressure oil supplied to afirst pilot chamber 22a serving as the pilot chamber, via thepilot valve 10. - The
check valve 21 allows the working oil to flow from thecontrol valve 6 to the rod-side pressure chamber 2a, while restricting the flow of the working oil from the rod-side pressure chamber 2a to thecontrol valve 6. That is to say, thecheck valve 21 prevents the working oil in the rod-side pressure chamber 2a from leaking and retains the load pressure, and keeps the stopped state of the arm 1. - The switching
valve 22 is disposed in abypass passage 23 that leads working oil on the side of the rod-side pressure chamber 2a with respect to thecheck valve 21 to the side of thecontrol valve 6 with respect to thecheck valve 21, by bypassing thecheck valve 21. The switchingvalve 22 switches an opened or closed state of thebypass passage 23 in accordance with the pilot pressure supplied to thefirst pilot chamber 22a, and controls the flow of the working oil in the firstmain passage 7 when extending thecylinder 2. - When pilot pressure is leaded to the
pilot chamber 6b of thecontrol valve 6, pilot pressure of identical pressure is leaded simultaneously to thefirst pilot chamber 22a. That is to say, when thecontrol valve 6 is switched to theextension position 6B, the switchingvalve 22 also opens. - Describing in more details, when no pilot pressure is leaded to the
first pilot chamber 22a, the switchingvalve 22 maintains a disconnected state by an biasing force of aspring 24, and thebypass passage 23 is disconnected. - When pilot pressure is leaded to the
first pilot chamber 22a and the switchingvalve 22 receives a force exceeding the biasing force of thespring 24 in the valve opening direction by the pilot pressure, the switchingvalve 22 opens and thebypass passage 23 is released. As a result, the working oil in the rod-side pressure chamber 2a is leaded from thebypass passage 23 to the firstmain passage 7 on the side of thecontrol valve 6 with respect to thecheck valve 21, via the switchingvalve 22. That is to say, the working oil in the rod-side pressure chamber 2a is leaded to thecontrol valve 6, by bypassing thecheck valve 21. - A
relief passage 25 branches from and is connected to an upstream of thecheck valve 21 on the firstmain passage 7. Therelief passage 25 disposes arelief valve 26 that opens when pressure in the rod-side pressure chamber 2a reaches a predetermined pressure and allows working oil to flow therethrough, and releases the working oil in the rod-side pressure chamber 2a. The working oil that passes through therelief valve 26 is discharged to the tank T via the dischargingpassage 27. Anorifice 28 is disposed on the dischargingpassage 27, and pressure upstream of theorifice 28 is leaded to asecond pilot chamber 22b. That is to say, the switchingvalve 22 also opens by the pressure of relief pressure oil leaded through therelief valve 26 to thesecond pilot chamber 22b. - A first
main relief valve 13 is connected on the side of thecontrol valve 6 with respect to thecheck valve 21 in the firstmain passage 7, and the secondmain passage 8 is connected to a secondmain relief valve 14. The firstmain relief valve 13 and the secondmain relief valve 14, when a large external force acts on the arm 1, release a high pressure occurring on the rod-side pressure chamber 2a and the counter rod-side pressure chamber 2b of thecylinder 2. - Next describes a structure of the
load retaining mechanism 20, with reference toFig. 3 . - The
check valve 21 is assembled in abody 30. Thebody 30 is formed having a slidinghole 30a, and in the slidinghole 30a, avalve element 31 of thecheck valve 21 is slidably assembled. The slidinghole 30a is formed penetrating through thebody 30. One end (upstream end) of the slidinghole 30a is connected to the firstmain passage 7 on the side of thecylinder 2 via aplug 32, and the other end (downstream end) thereof is connected to the firstmain passage 7 on the side of thecontrol valve 6 via aplug 33. - On an inner wall of the sliding
hole 30a, aseat portion 34 is formed, which decreases in diameter as it progresses downstream. Thevalve element 31 is constantly pressed in a direction sitting on theseat portion 34, by biasing force of aspring 35 disposed between thevalve element 31 and theplug 32. - The
check valve 21 maintains a closed state with respect to the working oil flowing from the firstmain passage 7 on the side of thecylinder 2. Moreover, thecheck valve 21 opens when thevalve element 31 receives a force exceeding the biasing force of thespring 35 by the pressure of the working oil flowing from the firstmain passage 7 on the side of thecontrol valve 6. - The switching
valve 22 is assembled inside thebody 30. Aspool hole 30b is formed in thebody 30, and aspool 36 is assembled slidably in thespool hole 30b. On a side of oneend plane 36a of thespool 36, aspring chamber 38 is defined by acap 37. Thespring chamber 38 communicates with a drain passage 40 (seeFig. 2 ) via adrain port 39a formed in aplug 39 that screws to an opening of thecap 37. Thedrain passage 40 communicates with a downstream of theorifice 28 in a discharging passage 27 (seeFig. 2 ) and connects to the tank T. - The
spring chamber 38 accommodates aspring 41 serving as an biasing member for biasing thespool 36. Moreover, thespring chamber 38 accommodates an annular firstspring holding member 42 whose end plane abuts one end plane of thespool 36, and an annular secondspring holding member 43 that abuts a tip surface of theplug 39 screwed to thecap 37. Thespring 41 is disposed in a compressed state between the firstspring holding member 42 and the secondspring holding member 43, and biases thespool 36 in the valve-closing direction via the firstspring holding member 42. - On a side of the
other end plane 36b of thespool 36, thepilot chambers piston hole 30c andcap 44. Thepiston hole 30c is formed in communication with thespool hole 30b. Thecap 44 closes thepiston hole 30c. Apiston 45 is inserted slidably inside thepilot chambers piston 45 includes a rear plane receiving pilot pressure, and applies thrust against the biasing force of thespring 41 to thespool 36 when the rea plane receives the pilot pressure. - The
pilot chambers piston 45 into afirst pilot chamber 22a facing the rear plane of thepiston 45 and asecond pilot chamber 22b facing the front plane of thepiston 45 and theother end plane 36b of thespool 36. Thefirst pilot chamber 22a is supplied with pilot pressure oil from thepilot valve 10 via apilot port 44a formed in thecap 44. Leaded to thesecond pilot chamber 22b is relief valve oil having passed through therelief valve 26 via the dischargingpassage 27. - The
piston 45 includes a slidingportion 45a whose outer circumferential surface slides along an inner circumferential surface of thepiston hole 30c, atip portion 45b facing theother end plane 36b of thespool 36, agroove portion 45c formed across the front plane of thepiston 45 in a radial direction, and aconduction path 46 that allows thefirst pilot chamber 22a to communicate with thesecond pilot chamber 22b. Thetip portion 45b is formed having a smaller diameter than that of the slidingportion 45a. Theconduction path 46 is provided pierced through the slidingportion 45a. - The
conduction path 46 includes anaxial direction passage 46a defined by a hole pierced through from an end plane of the slidingportion 45a on the side of thecap 44 to around a center of the slidingportion 45a towards thetip portion 45b in an axial direction, aradial direction passage 46b defined by a hole pierced through from a tip of theaxial direction passage 46a in a radial direction to penetrate through the slidingportion 45a, and anair removing throttle 46c defined by a hole provided at a joining part at the tip of theaxial direction passage 46a with theradial direction passage 46b. - When pilot pressure oil is supplied in the
first pilot chamber 22a via thepilot port 44a, the pilot pressure acts on the rear plane of the slidingportion 45a. This causes thepiston 45 to move forward, which makes thetip portion 45b contact theother end plane 36b of thespool 36 and make thespool 36 move. As such, thespool 36 receives the thrust of thepiston 45 generated based on the pilot pressure acting on the rear plane of thepiston 45, and moves in the valve-opening direction against the biasing force of thespring 41. - When the relief pressure oil that has passed through the
relief valve 26 is leaded in thesecond pilot chamber 22b via the dischargingpassage 27, the pressure of the relief pressure oil acts on theother end plane 36b of thespool 36. This causes thespool 36 to move in the valve-opening direction against the biasing force of thespring 41. Meanwhile, since the pressure of the relief pressure oil also acts on thepiston 45, thepiston 45 moves backwards and contacts thecap 44. - The
spool 36 stops at a position in which the biasing force of thespring 41 acting on oneend plane 36a is balanced with the thrust of thepiston 45 acting on theother end plane 36b, and an aperture of the switchingvalve 22 is defined in accordance with the stopped position of thespool 36. Thespool 36 moves in the valve-opening direction when the thrust of thepiston 45 is greater than the biasing force of thespring 41, and moves in the valve-closing direction when the biasing force of thespring 41 is greater than the thrust of thepiston 45. - The outer circumferential surface of the
spool 36 is partially cut off annularly, and apoppet portion 47, afirst land portion 48, and asecond land portion 49 are formed in the order from the tip side in the valve-opening direction. Thepoppet portion 47 has an outer diameter greater than those of thefirst land portion 48 and thesecond land portion 49, and is formed in a tapered manner with its outer diameter increasing as it advances in the valve-opening direction. - The inner circumferential surface of the
spool hole 30b is partially cut off annularly, and with this cut off parts and the outer circumferential surface of thespool 36, afirst pressure chamber 50, asecond pressure chamber 51, and athird pressure chamber 52 are formed in order from the tip side in the valve-opening direction. - The
body 30 is formed having afirst communication passage 53 that allows thefirst pressure chamber 50 to communicate with the firstmain passage 7, and asecond communication passage 54 that allows thethird pressure chamber 52 to communicate with the firstmain passage 7. Thefirst communication passage 53 communicates with a downstream of theseat portion 34 of thecheck valve 21 in the firstmain passage 7, and thesecond communication passage 54 communicates with an upstream of theseat portion 34 of thecheck valve 21 in the firstmain passage 7. Thefirst communication passage 53 and thesecond communication passage 54 form thebypass passage 23 together with thespool hole 30b. - The
first pressure chamber 50 constantly communicates with the firstmain passage 7 at downstream of theseat portion 34 of thecheck valve 21. Thesecond pressure chamber 51 is disconnected from thefirst pressure chamber 50 when thepoppet portion 47 is seated on an annular projectingportion 55 projecting annularly inside in the radial direction from the inner circumferential surface of thespool hole 30b. Thethird pressure chamber 52 communicates constantly with am upstream of theseat portion 34 of thecheck valve 21 in the firstmain passage 7. - A plurality of
notches 56 are formed on the outer circumference of thefirst land portion 48 of thespool 36. Thenotches 56 allow thethird pressure chamber 52 to communicate with thesecond pressure chamber 51 when thespool 36 moves in the valve-opening direction. Thesecond pilot chamber 22b is constantly communicated with thespring chamber 38 via aconduction hole 57 formed in the axial direction inside thespool 36, and athrottle passage 58. One end of theconduction hole 57 opens to thesecond pilot chamber 22b, and the other end is located in the vicinity of thespring chamber 38. - Here, operations of the switching
valve 22 is described with reference toFig. 3 to Fig. 5 , andFig. 6A and Fig. 6B . - As shown in
Fig. 3 , when no pilot pressure is leaded to thefirst pilot chamber 22a, thepoppet portion 47 that is formed in thespool 36 is pressed against the annular projectingportion 55 formed on the inner circumference of thespool hole 30b, by the biasing force of thespring 41. Therefore, the communication between thesecond pressure chamber 51 and thefirst pressure chamber 50 is disconnected, and the communication between thefirst communication passage 53 and thesecond communication passage 54 is disconnected. This hinders the working oil in the rod-side pressure chamber 2a of thecylinder 2 from flowing to the side of thecontrol valve 6 via thebypass passage 23. - As shown in
Fig. 4 , when pilot pressure is leaded to thefirst pilot chamber 22a and thespool 36 receives thrust of thepiston 45 greater than the biasing force of thespring 41, thespool 36 moves in the valve-opening direction against the biasing force of thespring 41. This causes thepoppet portion 47 to separate away from the annular projectingportion 55, and causes thethird pressure chamber 52 to communicate with thesecond pressure chamber 51 via the plurality ofnotches 56. Therefore, thesecond communication passage 54 communicates with thefirst communication passage 53 via thethird pressure chamber 52, thenotches 56, thesecond pressure chamber 51, and thefirst pressure chamber 50. This causes the working oil in the rod-side pressure chamber 2a to be leaded to the firstmain passage 7 on the side of thecontrol valve 6 via thenotches 56. - Furthermore, by the movement of the
spool 36, the opening of thethrottle passage 58 reaches an expandeddiameter portion 59 of thecap 37. In the expandeddiameter portion 59, the inner circumferential plane of thecap 37 is formed with a larger diameter. When the opening of thethrottle passage 58 reaches the expandeddiameter portion 59, thesecond pilot chamber 22b communicates with thespring chamber 38 via theconduction hole 57 and thethrottle passage 58. -
Fig. 6A is a partially enlarged view showing thepiston 45 ofFig. 4 in an enlarged manner. The inner diameter of thesecond pilot chamber 22b is slightly larger than the outer diameter of a slidingportion 45a of thepiston 45. In the state shown inFig. 6A , the opening of theradial direction passage 46b of thepiston 45 has not reached thesecond pilot chamber 22b. Therefore, the pilot pressure oil that is leaded to thefirst pilot chamber 22a remains in thefirst pilot chamber 22a without leaking into thesecond pilot chamber 22b. Therefore, in this state, the pilot pressure oil in thefirst pilot chamber 22a does not flow into thespring chamber 38 via theconduction hole 57 and thethrottle passage 58. - As shown in
Fig. 5 , when the pilot pressure that is leaded to thefirst pilot chamber 22a becomes large and thespool 36 moves to its full stroke position in the valve-opening position against the biasing force of thespring 41, the front plane of thepiston 45 contacts astep portion 60 formed at a borderline between thepiston hole 30c and thespool hole 30b. This causes thethird pressure chamber 52 to communicate with thesecond pressure chamber 51 with an opening area larger than that in the state ofFig. 4 . Thus, a flow rate of the working oil that is leaded from the rod-side pressure chamber 2a to the firstmain passage 7 on the side of thecontrol valve 6 via thebypass passage 23 increases. - Furthermore, as with
Fig. 4 , since the opening of thethrottle passage 58 faces the expandeddiameter portion 59, thesecond pilot chamber 22b is continuously maintained in the communicated state with thespring chamber 38 via theconduction hole 57 and thethrottle passage 58. -
Fig. 6B is a partially enlarged view showing thepiston 45 ofFig. 5 in an enlarged manner. As shown inFig. 6B , when thepiston 45 moves to the full stroke position, the opening of theradial direction passage 46b of thepiston 45 opens to thesecond pilot chamber 22b. This causes the pilot pressure oil leaded to thefirst pilot chamber 22a to be leaded to thesecond pilot chamber 22b via theaxial direction passage 46a and theradial direction passage 46b. Meanwhile, since the flow of the pilot pressure oil is throttled by theair removing throttle 46c provided between theaxial direction passage 46a and theradial direction passage 46b, the pilot pressure in thefirst pilot chamber 22a is maintained at a predetermined pilot pressure. - The pilot pressure oil that is leaded to the
second pilot chamber 22b is leaded to theconduction hole 57 inside thespool hole 30b via thegroove portion 45c formed on the front plane of thepiston 45. Furthermore, as shown inFig. 5 , the pilot pressure oil is leaded from theconduction hole 57 to thespring chamber 38 via thethrottle passage 58, and is discharged to thedrain passage 40 via thedrain port 39a. - Here, as shown in
Fig. 6A and Fig. 6B , when the stroke amount of thepiston 45 becomes equal to or more than a predetermined stroke amount, the opening of theradial direction passage 46b of thepiston 45 starts to open to thesecond pilot chamber 22b. This predetermined stroke amount is defined by a position that theradial direction passage 46b is formed. In the present embodiment, the predetermined stroke amount is set as a stroke amount slightly smaller than the stroke amount equivalent to a full stroke of thepiston 45. - Next described are operations of the
hydraulic control device 100 with reference toFig. 2 to Fig. 5 . - When the
control valve 6 is in theneutral position 6C, the working oil that is discharged by the pump 4 is not supplied to thecylinder 2. Meanwhile, no pilot pressure is leaded to thefirst pilot chamber 22a of the switchingvalve 22; accordingly, the switchingvalve 22 maintains the disconnected state, and thebypass passage 23 is disconnected. The firstmain passage 7 is maintained in a state disconnected by thecheck valve 21. This prevents the leaking of the working oil in the rod-side pressure chamber 2a, and the stopped state of the arm 1 is retained. - When the operation lever 9 is operated and the pilot pressure is leaded from the
pilot valve 10 to thepilot chamber 6a of thecontrol valve 6, thecontrol valve 6 switches to thecontraction position 6A by an amount in accordance with the pilot pressure. When thecontrol valve 6 switches to thecontraction position 6A, the pressure of the working oil that is discharged by the pump 4 causes thecheck valve 21 to open. As a result, the working oil that is discharged from the pump 4 is supplied to the rod-side pressure chamber 2a, and thecylinder 2 contracts. This causes the arm 1 to lift up in the direction of arrow A shown inFig. 1 . - When the operation lever 9 is operated and the pilot pressure is leaded from the
pilot valve 10 to thepilot chamber 6b of thecontrol valve 6, thecontrol valve 6 switches to theextension position 6B by the amount in accordance with the pilot pressure. Moreover, simultaneously to this, the pilot pressure is also leaded to thefirst pilot chamber 22a; accordingly, the switchingvalve 22 opens in accordance with the supplied pilot pressure. - The
bypass passage 23 is released by this, and thus the working oil in the rod-side pressure chamber 2a is leaded to thecontrol valve 6 by bypassing thecheck valve 21 from the firstmain passage 7, and is discharged from thecontrol valve 6 to the tank T. Moreover, the working oil that is discharged by the pump 4 is supplied to the counter rod-side pressure chamber 2b, and thus thecylinder 2 extends. This causes the arm 1 to descend in the direction of arrow B shown inFig. 1 . - Here, in the manufacturing stage of the hydraulic shovel, particularly in the stage in which the
load retaining mechanism 20 is attached to the hydraulic shovel and thepilot passage 15 is connected to thepilot port 44a of theload retaining mechanism 20, air is mixed inside thefirst pilot chamber 22a to which the pilot pressure is supplied. Moreover, air may also similarly mix therein after maintenance and long-term storage of the hydraulic shovel. - When the pilot pressure oil is leaded to the
first pilot chamber 22a of the switchingvalve 22 by the lever operation of the operator in this state, the pilot pressure in thefirst pilot chamber 22a varies due to the volume change of the air, and may cause a response delay in the movement of thespool 36. This may cause a decrease in the operability of thecylinder 2. - In order to remove the air from the
first pilot chamber 22a by discharging the air in thefirst pilot chamber 22a to thedrain passage 40 via thesecond pilot chamber 22b, a structure can be considered in which thefirst pilot chamber 22a constantly communicates with thesecond pilot chamber 22b. However, with such a structure, the pilot pressure oil in thefirst pilot chamber 22a will constantly drain to thedrain passage 40 even after the air is discharged upon movement of thespool 36 by a predetermined stroke amount or more. Therefore, the pilot pressure may become unstable. Particularly when performing an operation such as an inching operation in which lever operated amount by the operator is minute, this may cause a response delay or a variation in responsiveness in the opening and closing operation of the switchingvalve 22. - In the present embodiment, the
conduction path 46 that allows thefirst pilot chamber 22a to communicate with thesecond pilot chamber 22b is provided in thepiston 45. Furthermore, theconduction path 46 opens when the stroke amount of thepiston 45 becomes equal to or more than the predetermined stroke amount that is slightly smaller than the full stroke amount. - Accordingly, no pilot pressure oil in the
first pilot chamber 22a is leaded to thesecond pilot chamber 22b at the time of minute operation of the switchingvalve 22 where the stroke amount of thepiston 45 is small. Therefore, the response delay and variation in responsiveness are prevented in the opening and closing operation of the switchingvalve 22 when performing the inching operation. Furthermore, when it is not a slight operation, that is to say, when the stroke amount of thepiston 45 is large, the pilot pressure oil in thefirst pilot chamber 22a is leaded to thesecond pilot chamber 22b together with the air. Therefore, the air that is mixed into thefirst pilot chamber 22a is discharged. - According to the embodiment, the following effects are achieved.
- The switching
valve 22 includes aconduction path 46 that leads one part of the pilot pressure oil leaded to thefirst pilot chamber 22a, to thedrain passage 40. Theconduction path 46 communicates with thedrain passage 40 when thepiston 45 of the switchingvalve 22 moves by the predetermined stroke amount or more in the valve-opening direction. Therefore, at the time of slight operation in which the stroke amount of the switchingvalve 22 is small, the variation in the pilot pressure can be prevented, and when the stroke amount of the switchingvalve 22 is large, the air that is mixed in thefirst pilot chamber 22a can be discharged to thedrain passage 40. Thus, air removal of thefirst pilot chamber 22a is possible while holding down the effect on the responsiveness. - Furthermore, the switching
valve 22 includes thepiston 45 that presses thespool 36 in the valve-opening direction in receiving the pilot pressure in thefirst pilot chamber 22a, and theconduction path 46 that allows thefirst pilot chamber 22a to communicate with thesecond pilot chamber 22b is formed in thepiston 45. Therefore, the air removal can be performed without making the structure of the spool complex. - Furthermore, since the
conduction path 46 is pierced through the inside of thepiston 45, it is possible to prevent the pilot pressure oil from leaking via the outer circumference of thepiston 45 from theconduction path 46, before the stroke amount of thepiston 45 reaches the predetermined stroke amount. Thus, air removal of thefirst pilot chamber 22a is possible while securely suppressing the effect on the responsiveness. - Next describes a second embodiment, with reference to
Fig. 7 ,Fig. 8 , andFig. 9A to Fig. 9C . - In the present embodiment, the structure of a
conduction path 146 differs from the first embodiment. Moreover, in the first embodiment, theconduction hole 57 that allows thesecond pilot chamber 22b to communicate with thespring chamber 38 is formed inside thespool 36, whereas in the present embodiment, aconduction hole 157 is newly formed in thebody 30. One end (downstream end) of thisconduction hole 157 is connected to athrottle passage 158 that allows the inside of thecap 37 to communicate with the outside of thecap 37 screwed to thebody 30. This makes thesecond pilot chamber 22b communicate with thedrain port 39a via theconduction hole 157, thethrottle passage 158 and thespring chamber 38. - As shown in
Fig. 7 , theconduction path 146 is formed on the outer circumferential surface of the slidingportion 45a of thepiston 45.Fig. 9A is a partially enlarged view showing thepiston 45 ofFig. 7 in an enlarged manner. Theconduction path 146 includes aspiral groove 146a serving as a groove formed in a spiral form on the outer circumferential surface of the slidingportion 45a of thepiston 45, and asmall diameter portion 146b serving as a groove formed on the outer circumferential surface of the slidingportion 45a. Thesmall diameter portion 146b is connected to a terminal of thespiral groove 146a on the side of the piston front plane (left side inFig. 9A ). Thesmall diameter portion 146b has a smaller diameter than that of the outer circumferential surface of the slidingportion 45a. - A cross sectional shape of the
spiral groove 146a may be formed rectangular as shown inFig. 9B , or may be formed in a V-shape as shown inFig. 9C . Thespiral groove 146a is sufficiently small in its cross section, and also functions as a throttle. - As shown in
Fig. 7 , when no pilot pressure is leaded to thefirst pilot chamber 22a, thepiston 45 does not move. Therefore, thesmall diameter portion 146b does not open to thesecond pilot chamber 22b. Thus, the pilot pressure oil in thefirst pilot chamber 22a is not leaded to thesecond pilot chamber 22b. - As shown in
Fig 8 , when the pilot pressure that is leaded to thefirst pilot chamber 22a becomes large and thepiston 45 moves to the full stroke position, thesmall diameter portion 146b of thepiston 45 opens to thesecond pilot chamber 22b. This causes the pilot pressure oil leaded to the first pilot chamber to be leaded to thesecond pilot chamber 22b via thespiral groove 146a and thesmall diameter portion 146b. Meanwhile, the flow of the pilot pressure oil is throttled by a throttle effect of thespiral groove 146a; accordingly, the pilot pressure in thefirst pilot chamber 22a is maintained at the predetermined pilot pressure. - The pilot pressure oil that is leaded to the
second pilot chamber 22b is leaded to thespring chamber 38 via theconduction hole 157 formed in thebody 30 and thethrottle passage 158 formed in thecap 37, and is leaded to thedrain passage 40 via thedrain port 39a. - As with the first embodiment, when the stroke amount of the
piston 45 becomes equal to or more than a predetermined stroke amount, thesmall diameter portion 146b of thepiston 45 starts to open to thesecond pilot chamber 22b. This predetermined stroke amount is defined by the position that thesmall diameter portion 146b is formed. In the present embodiment, the predetermined stroke amount is set as a stroke amount slightly smaller than the stroke amount equivalent to a full stroke of thepiston 45. - According to the above embodiment, the following effects are achieved.
- Since the
conduction path 146 is formed on the outer circumferential surface of thepiston 45, theconduction path 146 can be formed just by forming a groove on the outer circumferential surface of thepiston 45 with an end mill or like device. This facilitates the forming of theconduction path 146, and allows for reducing manufacturing costs. - Next describes a third embodiment, with reference to
Fig. 10 andFig. 11 . - In the first embodiment, the
spool 36 and thepiston 45 are formed as separate bodies, whereas in the present embodiment, thepiston 45 and thepiston hole 30c are omitted, and aspool hole 230b and aspool 236 extend in the axial direction. That is to say, thespool hole 230b communicates with thefirst pilot chamber 22a, and theother end plane 236b of thespool 236 faces thefirst pilot chamber 22a. - Moreover, in the first embodiment, the
conduction hole 57 that allows thesecond pilot chamber 22b to communicate with thespring chamber 38 is formed inside thespool 36, whereas in the present embodiment, aconduction hole 257 is newly formed in thebody 30. One end (downstream end) of thisconduction hole 257 is connected to athrottle passage 258 that allows the inside of thecap 37 to communicate with the outside thecap 37 screwed to thebody 30. Moreover, in the first embodiment, the working oil that has passed through therelief valve 26 is leaded to thesecond pilot chamber 22b, whereas in the present embodiment, instead of thepilot chamber 22b, alarge diameter portion 61 is newly provided, which portion is formed by annularly cutting off the inner circumferential surface of thespool hole 230b. Since the internal diameter of thelarge diameter portion 61 is larger than the outer diameter of thespool 36, the working oil that has passed through therelief valve 26 is constantly leaded to theconduction hole 257 regardless of the axial direction position of thespool 236, and is leaded to thedrain port 39a via thethrottle passage 258 and thespring chamber 38. - Furthermore, since the
large diameter portion 61 opens to the outer circumference of thespool 36, thespool 236 does not receive force in the axial direction from the working oil having passed through therelief valve 26. Therefore, the hydraulic circuit diagram of the present embodiment is shown inFig. 14 , instead ofFig. 2 that shows the hydraulic circuit diagram of the first embodiment. That is to say, the working oil that has passed through therelief valve 26 is constantly discharged to the tank T, without acting on the switchingvalve 22. InFig. 14 , members having the same functions as those inFig. 2 are provided with identical reference signs. - As shown in
Fig. 10 , theconduction path 246 is pierced through the inside of thespool 236. More specifically, theconduction path 246 includes anaxial direction passage 246a defined by a hole pierced through in the axial direction from theother end plane 236b serving as a pressure receiving plane of thespool 36 to an oneend plane 236a, aradial direction passage 246b defined by a hole pierced through in a radial direction from the tip of theaxial direction passage 246a and penetrating through thespool 236, and anair removing throttle 246c defined by a hole provided at a joining part with theradial direction passage 246b at the tip of theaxial direction passage 246a. - As shown in
Fig. 10 , when no pilot pressure is leaded to thefirst pilot chamber 22a, thespool 236 does not move. Therefore, the opening of theradial direction passage 246b does not open to thelarge diameter portion 61. Thus, no pilot pressure oil in thefirst pilot chamber 22a is leaded to thelarge diameter portion 61. - As shown in
Fig. 11 , when the pilot pressure that is leaded to thefirst pilot chamber 22a becomes large and thespool 236 moves to the full stroke position, the opening of theradial direction passage 246b of thespool 236 opens to thelarge diameter portion 61. This allows the pilot pressure oil leaded to thefirst pilot chamber 22a to be leaded to thelarge diameter portion 61 via theconduction path 246. Meanwhile, since the flow of the pilot pressure oil is throttled by theair removing throttle 246c, the pilot pressure in thefirst pilot chamber 22a is maintained at the predetermined pilot pressure. - The pilot pressure oil that is leaded to the
large diameter portion 61 is leaded to thespring chamber 38 via theconduction hole 257 formed in thebody 30 and thethrottle passage 258 formed in thecap 37, and is leaded to thedrain passage 40 via thedrain port 39a. - As with the first embodiment, when the stroke amount of the
spool 236 becomes equal to or more than a predetermined stroke amount, theradial direction passage 246b of thespool 236 starts to open to thelarge diameter portion 61. This predetermined stroke amount is defined by the position that theradial direction passage 246b is formed. In the present embodiment, the predetermined stroke amount is set to a stroke amount slightly smaller than a stroke amount equivalent to the full stroke of thespool 236. - According to the above embodiment, the following effects are achieved.
- The
other end plane 236b of thespool 236 receives the pilot pressure from thefirst pilot chamber 22a and thespool 236 moves in the valve-opening direction, and thus there is no need to provide a piston for receiving the pilot pressure. Therefore, the number of parts can be reduced. - Furthermore, since the
conduction path 246 is pierced through inside thespool 236, it is possible to prevent the pilot pressure oil from leaking via the outer circumference of thespool 236 from theconduction path 246 before the stroke amount of thespool 236 reaches the predetermined stroke amount. Thus, air removal of thefirst pilot chamber 22a is possible while securely suppress the effect on the responsiveness. - Furthermore, since the
conduction hole 257 is formed in thebody 30, this allows for simplifying the structure of thespool 236, and allows for reducing manufacturing costs. - Next describes a fourth embodiment with reference to
Fig. 12 andFig. 13 . - In the present embodiment, the structure of a
conduction path 346 differs from that of the third embodiment, however other structures are identical to the third embodiment. - As shown in
Fig. 12 , theconduction path 346 is formed on the outer circumferential surface of thespool 36. Theconduction path 346, as with theconduction path 146 shown inFig. 9A , includes aspiral groove 346a serving as a groove formed in a spiral form on the outer circumferential surface of thespool 36, and asmall diameter portion 346b serving as a groove formed on the outer circumferential surface of thespool 36. Thesmall diameter portion 346b is connected to a terminal of thespiral groove 346a on the stroke side (left side inFig. 12 ) of thespool 36. Thesmall diameter portion 346b has a smaller diameter than that of the outer circumferential surface of thespool 336. - The cross section of the
spiral groove 346a may be formed in a rectangular shape as with the spiral groove 14a shown inFig. 9B , or may be formed in a V-shape as with the spiral groove 14a shown inFig. 9C . Thespiral groove 346a is sufficiently small in its cross section, and also functions as a throttle. - As shown in
Fig. 12 , when no pilot pressure is leaded to thefirst pilot chamber 22a, thespool 336 does not move. Therefore, thesmall diameter portion 346b does not open to thelarge diameter portion 61. Thus, no pilot pressure oil in thefirst pilot chamber 22a is leaded to thelarge diameter portion 61. - As shown in
Fig. 13 , when the pilot pressure that is leaded to thefirst pilot chamber 22a becomes large and thespool 336 moves to the full stroke position, thesmall diameter portion 346b of thespool 336 opens to thelarge diameter portion 61. This causes the pilot pressure oil leaded to thefirst pilot chamber 22a to be leaded to thelarge diameter portion 61 via thespiral groove 346a and thesmall diameter portion 346b. Meanwhile, since the flow of the pilot pressure oil is throttled by the throttle effect of thespiral groove 346a, the pilot pressure in thefirst pilot chamber 22a is maintained at the predetermined pilot pressure. - The pilot pressure oil that is leaded to the
large diameter portion 61 is leaded to theconduction hole 257 formed in thebody 30, and is discharged to thedrain passage 40 via thethrottle passage 258 formed in thecap 37, thespring chamber 38, and thedrain port 39a. - As with the third embodiment, when the stroke amount of the
spool 336 becomes equal to or more than a predetermined stroke amount, thesmall diameter portion 346b of thespool 36 starts to open to thelarge diameter portion 61. This predetermined stroke amount is defined by the position that thesmall diameter portion 346b is formed. In the present embodiment, the predetermined stroke amount is set to a stroke amount slightly smaller than a stroke amount equivalent to the full stroke of thespool 336. - According to the above embodiment, the following effects are achieved.
- The
conduction path 346 is formed on the outer circumferential surface of thespool 336. Accordingly, theconduction path 346 can be formed just by forming a groove on the outer circumferential surface of thespool 336 with an end mill or like device. This facilitates the forming of theconduction path 346, and allows for reducing manufacturing costs. - Embodiments of this invention were described above, but the above embodiments are merely examples of applications of this invention, and the technical scope of this invention is not limited to the specific constitutions of the above embodiments.
- For example, in the above embodiments, cases in which working oil is used as the working fluid is exemplified; however, the working fluid may be liquid other than oil, for example water or an alternate water-soluble liquid.
- Furthermore, in the above embodiments, the
spring 41 is exemplified as the biasing member, however this may be any other extendable member that can bias the spool. - This application claims priority based on Japanese Patent Application No.
2014-205870
Claims (7)
- A fluid pressure control device comprising:a cylinder configured to extend and contract by working fluid supplied from a pump to drive a load;a control valve configured to switch supply/discharge of the working fluid to/from the cylinder to control the extending and contracting of the cylinder;a pilot valve configured to lead pilot pressure to the control valve;a main passage configured to connect the control valve and a load-side pressure chamber of the cylinder to which load pressure acts due to the load when the control valve is in a neutral position; anda load retaining mechanism disposed on the main passage and configured to retain load pressure in the load-side pressure chamber when the control valve is in the neutral position,wherein the load retaining mechanism comprises:a check valve configured to allow the working fluid to flow only from the control valve to the load-side pressure chamber;a bypass passage configured to lead the working fluid in the load-side pressure chamber to the control valve by bypassing the check valve; anda switching valve disposed on the bypass passage and configured to switch an opened or closed state of the bypass passage,the switching valve comprises:a pilot chamber to which pilot pressure is leaded via the pilot valve;a spool configured to move in a valve-opening direction in accordance with the pilot pressure in the pilot chamber;a biasing member configured to bias the spool in a valve-closing direction; anda conduction path configured to lead one part of a pilot pressure fluid leaded to the pilot chamber, to a drain passage,the conduction path is configured to communicate with the drain passage, when the switching valve moves by a predetermined stroke amount or more in the valve-opening direction.
- The fluid pressure control device according to claim 1, wherein
the switching valve includes a piston housed slidably within the pilot chamber and is configured to receive pilot pressure leaded via the pilot valve to press the spool in the valve-opening direction, and
the conduction path is formed in the piston and is configured to communicate with the drain passage when the piston receives pilot pressure and moves by the predetermined stroke amount or more. - The fluid pressure control device according to claim 2, wherein
the conduction path is a hole pierced through the piston. - The fluid pressure control device according to claim 2, wherein
the conduction path is a groove formed on an outer circumferential surface of the piston. - The fluid pressure control device according to claim 1, wherein
the spool includes a pressure-receiving plane configured to receive pilot pressure leaded to the pilot chamber, and
the conduction path is formed on a side of the pressure-receiving plane of the spool, and is configured to communicate with the drain passage when the spool receives pilot pressure and moves by the predetermined stroke amount or more. - The fluid pressure control device according to claim 5, wherein
the conduction path is a hole pierced through the spool. - The fluid pressure control device according to claim 5, wherein
the conduction path is a groove formed on an outer circumferential surface of the spool.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP2014205870A JP6397715B2 (en) | 2014-10-06 | 2014-10-06 | Fluid pressure control device |
PCT/JP2015/078391 WO2016056564A1 (en) | 2014-10-06 | 2015-10-06 | Fluid pressure control device |
Publications (3)
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EP3205888A1 true EP3205888A1 (en) | 2017-08-16 |
EP3205888A4 EP3205888A4 (en) | 2018-06-27 |
EP3205888B1 EP3205888B1 (en) | 2020-03-25 |
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EP15849172.0A Active EP3205888B1 (en) | 2014-10-06 | 2015-10-06 | Fluid pressure control device |
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EP (1) | EP3205888B1 (en) |
JP (1) | JP6397715B2 (en) |
KR (1) | KR102372065B1 (en) |
CN (1) | CN107076175B (en) |
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WO (1) | WO2016056564A1 (en) |
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EP4030067A1 (en) * | 2021-01-15 | 2022-07-20 | XCMG European Research Center GmbH | Hydraulic control for hydraulic machines |
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JP6600386B1 (en) * | 2018-07-06 | 2019-10-30 | Kyb株式会社 | Valve device |
JP7030678B2 (en) * | 2018-12-21 | 2022-03-07 | 株式会社クボタ | Control valve |
JP2023091435A (en) * | 2021-12-20 | 2023-06-30 | 株式会社クボタ | Control valve and work machine including the same |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
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EP0197467B1 (en) * | 1985-04-11 | 1992-01-29 | Beringer-Hydraulik AG | Leak-free load control and holding valve |
JP3727828B2 (en) * | 2000-05-19 | 2005-12-21 | 日立建機株式会社 | Pipe break control valve device |
JP3776744B2 (en) * | 2001-04-20 | 2006-05-17 | 新キャタピラー三菱株式会社 | Air bleeding structure of pilot operated control valve |
JP3915622B2 (en) * | 2002-07-30 | 2007-05-16 | コベルコ建機株式会社 | Load holding device for hydraulic actuator circuit |
JP2004132411A (en) * | 2002-10-09 | 2004-04-30 | Kayaba Ind Co Ltd | Hydraulic control device |
JP4473322B2 (en) * | 2008-03-31 | 2010-06-02 | 株式会社カワサキプレシジョンマシナリ | Holding control valve |
JP5916450B2 (en) * | 2012-03-15 | 2016-05-11 | Kyb株式会社 | Switching valve |
US20140174063A1 (en) * | 2012-12-20 | 2014-06-26 | Caterpillar Inc. | Hydraulic system for controlling a work implement |
JP5948260B2 (en) * | 2013-01-24 | 2016-07-06 | Kyb株式会社 | Fluid pressure control device |
JP5571809B2 (en) * | 2013-02-04 | 2014-08-13 | カヤバ工業株式会社 | Brake system |
-
2014
- 2014-10-06 JP JP2014205870A patent/JP6397715B2/en active Active
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2015
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- 2015-10-06 WO PCT/JP2015/078391 patent/WO2016056564A1/en active Application Filing
- 2015-10-06 EP EP15849172.0A patent/EP3205888B1/en active Active
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EP4030067A1 (en) * | 2021-01-15 | 2022-07-20 | XCMG European Research Center GmbH | Hydraulic control for hydraulic machines |
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DK3205888T3 (en) | 2020-04-27 |
CN107076175B (en) | 2019-01-18 |
CN107076175A (en) | 2017-08-18 |
EP3205888A4 (en) | 2018-06-27 |
EP3205888B1 (en) | 2020-03-25 |
JP2016075341A (en) | 2016-05-12 |
KR102372065B1 (en) | 2022-03-07 |
JP6397715B2 (en) | 2018-09-26 |
WO2016056564A1 (en) | 2016-04-14 |
KR20170063621A (en) | 2017-06-08 |
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